In the manufacture of concrete blocks, it is known to split a cured composite block module along one or more splitting planes to provide an irregular surface to the block.
It is also known to form such a split-type block by utilizing a mold that has a number of projections extending inwardly into the cavity. Such a method and mold are shown in my U.S. Pat. No. 5,078,940 issued Jun. 7, 1992, which is herein incorporated by reference. Molds such as that shown in the '940 patent utilize projections and a lip to form the irregular face on the block. As the concrete block is stripped from the mold, concrete collects on and between the projections and the irregular pattern is formed. It has been found that excessive amounts of concrete would collect on and between the projections and the lip, thus increasing the amount of force needed to strip the concrete block from the mold. This increased force did not present an insurmountable problem in single face blocks, but in multiple face blocks stripping was made very difficult, if not impossible.
The present invention eliminates any spaces or gaps between the projections and the lip for the concrete to gather in, thus making stripping of the concrete block much easier. It has also been found that with the use of this improved mold, both the feed time and the finish time can be increased, resulting in a superior product.
It has further been realized that the amount of material wasted during forming of the block can be reduced by as much as 50 percent.
It is a general object of the present invention to provide a block forming mold which has improved stripping ability, and is capable of more quickly and efficiently forming an irregular split-type block surface.
It is one object of the present invention to provide a block forming mold which markedly reduces wasted block material.
It is an additional object of the present invention to provide a block forming mold which lessens disturbance to the block by reducing friction during stripping and contributes to a decrease in cracking of the formed block.
It is a further object of the present invention to provide a block forming mold which enables the formation of a stronger, harder product exceeding increased use specifications.
It is also an object of the present invention to provide a block forming mold which produces a block which is cleaner in appearance and dimensionally correct.
In one aspect of the invention, a mold is provided for forming concrete block. The mold includes a plurality of interconnected vertical walls defining a block material forming cavity having a top opening and a bottom opening with at least one of the walls having a plurality of spaced projections extending inwardly from the wall into the cavity, and a lip at a bottom of the wall beneath the lowermost of the projections extending inwardly into the cavity. The lip has a top surface, a bottom surface and an inwardly extending lip extension disposed along the bottom surface. The invention is improved with the lip being formed with an upper vertical inner surface extending from the top surface to the lip extension. The invention is further improved with the lowermost of the projections having a bottom surface in abutment with the top surface of the tip, and a vertical inner surface coplanar with the upper vertical inner surface of the lip.
In another aspect of the invention, a mold used in a concrete block forming process includes a plurality of interconnected vertical walls defining a cavity having a top opening and a bottom opening adapted to receive concrete block forming material containing aggregate through the top opening, and to discharge formed block material in the form of the concrete block having a length, a width, and a height. At least one of the walls has a number of spaced projections extending inwardly from the at least one wall into the cavity. The at least one wall further includes a lip at a bottom of the wall beneath the lowermost of the projections extending inwardly into the cavity with the lip having a top surface and an inwardly extending lip extension disposed along a bottom surface of the lip. The lip is formed with an upper vertical surface extending from the top surface of the lip to the lip extension. The lowermost of the projections has a bottom surface in abutment with the top surface of the lip, and a vertical inner surface coplanar with the upper vertical surface of the lip. A shoe is engaged with an upper surface of the block forming material and is mounted for sliding movement relative to the vertical walls during the concrete block forming process. The shoe has at least one edge adjacent the projections and is spaced from the lip extension to define a surfacing gap through which waste material from the concrete block forming process will fall. The surfacing gap is determined substantially by a largest size of the aggregate in the block forming material, and the height of the concrete block to be formed.
Various other features, object and advantages of the invention will be made apparent from the following description taken together with the drawings.